The mating calls of Bufo viridis populations from Israel were studied and compared with that of a Central-European population in order to evaluate their nature, variation and evolutionary origin. In Israeli Bufo viridis, call duration, pulse duration and interpulse interval are negatively correlated with temperature, whereas fundamental frequency is negatively correlated with body size. The Israeli and Central-European Bufo viridis are almost identical in call duration, pulse number, pulse duration and pulse rate. They differ slightly but significantly in interpulse interval and more obviously, in their fundamental frequency. The latter is correlated with body size. Since Israeli Bufo viridis are much larger than the Central-European ones, their fundamental frequency is distinctly lower.
Bufo viridis illustrates a case in which variation in the fundamental frequency of the mating call is probably largely an incidental product of adaptive differentiation of body size to the humidity index.